The Korean title "Ajeossi" means "Mister" in English.
The primary weapon Ramrowan uses is a fixed-blade karambit. Specifically, the model featured throughout the film is a "Steel Tiger" Karambit made by Cold Steel; a Ventura, California based weapons manufacturer and seller.
The card that Jeong So-mi (Sae-ron Kim) gives Cha Tae-sik (Bin Won) is a Korean Yu-Gi-Oh! (2000) Trading Card. Though the card game itself is real, the card she gives him, Dark Knight, is fictional. Notice how the card has the color border of orange, yet it has a lore written on it, which is only on normal monster cards with a yellow border. Cards with an orange border have effects instead.